Since miniaturization of semiconductor elements has been accelerated in recent years, it has become necessary when performing a semiconductor circuit simulation to calculate a temperature increase in an element due to self-heating, especially a local temperature increase in an element, using a device model.
For example, in the case of a field effect transistor (FET), the self-heating occurs mainly at an edge of a gate electrode terminal between a gate and a drain, and the temperature of the edge of the gate electrode terminal and between the gate and the drain increases locally. As a result, the temperature of a drain resistor becomes higher than another model parameter.
A technique of a device model for simulating the self-heating as described above is disclosed (for example, Non Patent Literature 1). FIG. 7 is a view showing the technique of Non Patent Literature 1. As shown in FIG. 7, a device model of Non Patent Literature 1 includes an electrical model describing the electrical characteristics in consideration of a temperature change in an element and a thermal model describing the thermal characteristics of an element. It is thereby possible to calculate the electrical characteristics in consideration of a temperature increase in an element due to self-heating.
Further, a technique of a semiconductor circuit simulation using the above-described device model is also disclosed (for example, Patent Literature 1). In this technique, the above-described device model is used as a device model of all elements constituting a circuit in order to calculate a temperature increase in elements due to self-heating. Further, a thermal resistance value between two elements where a heat exchange occurs is calculated, and the thermal resistance value is inserted between thermal models of the device model corresponding to the two elements.
The heat exchange model is a thermal model that represents the giving and receiving of heat between elements. In this manner, according to the technique of Patent Literature 1 described above, it is possible to calculate a temperature increase in an element in consideration of not only a temperature increase in a single element due to self-heating but also an exchange of heat between elements.
Further, in relation to the semiconductor circuit simulation using the simulation circuit including the device model and the heat exchange model, a technique that models a physical phenomenon of a thermal noise and approximates a simulation value of noise characteristics at an actual measurement value by use of a gate resistor is also disclosed (for example, Patent Literature 2).